C# suggestions are replacing subsequent text in VS Code. Why?

My problem is that when I'm creating a variable, let's say int, and later I want to add the public modifier the word int gets deleted (I think the reason is due to the C# extension). This would not be a problem if this didn't happen when I press space.

When I press space, I should be able to not only accept the intellisense suggestion (in this case "public") but also add a space between the suggestion and the word that was before. This wasn't an issue before but VS Code and the C# extension had an update this week that brought this awful change.

Any suggestion of how can I solve this problem?

I tried adding "editor.suggest.insertMode": "insert" in settings.json, but apparently that's not where the problem is.

TL;DR This is a bug in the C# extension. A purported fix was released in version 1.26.0 (source). Though apparently it has broken again in v2.0.357.

I googled "site:github.com/dotnet/vscode-csharp/issues replace" and found @id:editor.suggest.insertMode not honored #5801. The description of the issue there seems to match what you have described. You can give the issue ticket a thumbs up to show support for it, and subscribe to it to get notified about discussion and progress. Please avoid making noisy comments like "+1". I'm subscribed to the issue ticket and will update this answer post as new information arrives.

Some sort of behaviour about completions was changed in VS Code 1.79 that has caused some extensions to have this different behaviour. VS Code is recommending that the issues be fixed on the extension side of things. See also Completion trigger behavior on word start characters changed in 1.79 #185286.

Based on VS code docs
What you can do is set the following setting to false:

"editor.acceptSuggestionOnCommitCharacter": false